The application relates to a decryption device, method for decrypting and method and system for secure data transmission.
For secure communication of an electronic document over a communication network, the document can be encrypted in a manner that only an intended receiver of the document can decrypt the document. For encrypting and decrypting documents, several cryptography techniques are known. Techniques of cryptography may generally be divided into two groups: symmetric-key cryptography and public-key cryptography.
In symmetric-key cryptography, a sender and receiver of a document share the same key for encryption and decryption of the document. The key must be kept secret to parties other than the sender and the receiver in order to securely communicate the document.
In public-key cryptography, a pair of keys including a public key and a private key is employed for encryption and decryption of the document. The public key and its corresponding private key are different, separate keys but are mathematically linked to each other. The public key may be made available to the public but the private key must be kept secret to parties other than the owner of the key pair. Thus, the private key may be also referred to as a secret key. The sender of a document can encrypt the document using the public key of the receiver of the document, send the encrypted document to the receiver and the receiver can decrypt the encrypted document with his/her private key.
Either in symmetric-key cryptography or public-key cryptography, encryption of the document may be performed within a secure environment of the sender of the document. Further, the decryption of the document may be performed within a secure environment of the receiver of the document. For example, when electronically communicating via email, the secure environments of the sender and the receiver may be, for example, inside office buildings with secure intranets protected by firewall software from malicious access via the Internet. The document may be transmitted (e.g. sent via email) outside the secure environment of the sender only after encryption of the document. Further, the decryption of the document may be performed only after the encrypted document arrives in the secure environment of the receiver (e.g. received via email). In other words, the document would have encrypted content when the document is outside the secure environments of the sender and the receiver. Thus, even if a third party intercepts the document during transmission, the third party would not be able to understand the content of the document since its content is encrypted.
In some circumstances, further improvement of the security in communicating a document may be required.